Design for the Environment/Grocery Bags

Since 1977, the grocery bag has become an integral aspect of retail activity in North America. However, in recent times, a shift in societal values towards a greater regard for the environment has seen the conventional plastic bag come under scrutiny. This conventional bag is derived from the material polyethylene, a material that itself comes from petroleum and natural gas resources. One way of improving the environmental situation and to adhere to new guidelines on plastic bag use is to introduce new technologies for biodegradable bags. These bags, made of materials such as Mater-Bi and PHA, have the ability of quickly breaking down into its elemental components because of their plant-based raw material composition. This study analyzes the different functional characteristics, and societal and economic impacts of the polyethylene, Mater-Bi, and PHA grocery bags. More importantly, a detailed analysis of the environmental impacts is performed, using a qualitative Streamlined Life Cycle Assessment, and a quantitative Economic Input-Output Life Cycle Assessment with recommendation on the future grocery bag needs that will adhere to the ever increasing government pressure to reduce environmental effects.

Highlights

Baseline: Polyethylene Plastic Bags

Polyethylene Summary
Component	Polyethylene
Raw Material	Petroleum
Plastic Grading	Non-biodegradable
Cost	US $1-3/kg
Weight	7g/bag
SLCA Score	63

Conventional plastic bags are manufactured from polyethylene, a polymer extracted from crude oil or natural gas, through Blown Film Extrusion. The common types of polyethylene used to make these bags are linear low density polyethylene, low density polyethylene, and high density polyethylene. In the Blown Film Extrusion process, polyethylene resin is melted and extruded through a vertical circular die to form a thin walled tube. The tube is inflated to form a balloon shape as air is introduced into the tube and cooled. A plastic bag is formed from the width of a sealed section of the tube. Retailer logos are also printed on the bag. This process results in bags that are stronger, lighter, and cheaper to produce than paper bags. They are also waterproof and weigh approximately six to seven grams, with an ability to carry a mass of twenty kilograms. This allows plastic grocery bags to be reused to carry other items or for disposal as garbage bags.

The premanufacture of plastic bags create significant impact as polyethylene must be extracted from crude oil or natural gas. Crude oil refinery releases toxic pollutants in forms of solid, liquid and gaseous. Solid pollution which can occur due to leaks or spills during the transport process include include spent catalysts or coke dust, tank bottoms, and sludges from the treatment processes. Moreover, the refinery process can potentially contaminate ground water and surface water within its surrounding area. This wastewater may contain oil residuals or other hazardous wastes. Although the water treatment processes can limit the amount of sulfides, ammonia, suspended solids and other hazardous substances, all of which may be present in the wastewater, surface bodies of water may develop a high concentration of these substances over time. Gaseous pollutants are also released in this process including toluene, ethylbenzene, xylene, nitrogen oxides(NO_x),carbon monoxide (CO), hydrogen sulfide (H₂S), and sulfur dioxide (SO₂) all of which are hazardous to the health of the environment and human beings.

Recycling and disposal of plastic bags also create significant concerns on the environment. In the Greater Toronto Area, plastic bags represent less than one percentage of residential solid waste by weight . However, plastic bags require approximately 1000 years to decompose [26]. Plastic bag recycling programs are available in many provinces in Canada including Ontario, Quebec and British Columbia . On average only one to three percentage of the six billion plastic bags used in Canada is recycled every year . Furthermore plastic bags made from different types of polyethylene cannot be mixed in the recycling process and therefore must be sorted prior to the recycling process. The sorting process is labour intensive and thus the cost of recapturing and recycling plastic bags can be expensive in Canada. Therefore, nearly all plastic bags are sent to landfill or incineration as solid waste.

Alternative: Mater-Bi Plastic Bags

Mater-Bi Summary
Components	Cornstarch, PCL
Raw Materials	Corn, Petroleum
Plastic Grading	Biodegradable
Cost	US $2-8/kg
Weight	9g/bag
SLCA Score	84

Novamont is a leading bioplastic manufacturer in Europe and offers starch-based Mater-Bi products extracted from agricultural raw materials. Its facility in Terni, Italy has a production capacity of 60,000 metric tons as of 2008 for 10 different film grades. Mater-Bi includes a wide range of starch-based bioplastic materials derived from cornstarch and vegetable oil additives. It also contains polycaprolactone (PCL), a biodegradable synthetic aliphatic polyester used to enhance barrier properties and reduce costs. It can be processed through similar steps as polyethylene and offers the primary benefit of compostability in a wide-range of conditions, from home composting to fermenting reactors.

For the premanufacture of Mater-Bi, corn, petroleum, and water are the primary resources extracted. Petroleum oil, a non-renewable resource used for the PCL polyester component, requires an energy-intense extraction process with high greenhouse gas emissions. Novamont is in the process of replacing PCL with a vegetable oil polyester in its Origo-Bi line. One film grade of Mater-Bi currently has 26% starch-74% PCL and produces one kilogram from 0.5 kilograms of cornstarch and 1.4 kilograms of PCL. High energy is required during the manufacturing of the thermoplastic starch component in Mater-Bi pellets. Processing of pellets is comparable to the technology used to produce polyethylene bags and also utilizes Blown Film Extrusion. Mater-Bi shopping bags, however, require thirty percent more resin than polyethylene. Greenhouse gases, acidication, and eutrophication are minimized in manufacturing as reported in Novamont’s Environmental Product Declaration.

The Mater-Bi biopolymer resin must be transported overseas from its factory in Italy to bag processors before wholesale and distribution to supermarkets in North America, leading to further petroleum use and greenhouse gas emissions. During end of life, the major environmental benefit of Mater-Bi is its reduced energy and management required for compost separation and biodegrades within six months to leave no solid residue, thereby reducing contamination. The higher quality greenhouse gas emissions are reduced compared to polyethylene bags as carbon dioxide absorbed during the growth of corn plants is released back from biomass. Overall emissions are highest in the end phase as waste bags are typically landfilled in North America, whereas they are incinerated in Europe to reduce solid residue and produce energy.

Alternative: PHA Plastic Bags

PHA Summary
Components	Sugar, Bacteria
Raw Materials	Corn
Plastic Grading	Biodegradable
Cost	US $5-16/kg
Weight	5g/bag
SLCA Score	87

One biodegradable copolyester produced by bacterial fermentation, termed polyhydroxyalkanoates (PHA), is synthesized in the bodies of bacteria, such as Alcaligenes eutrophus, which are fed with glucose extracted from sugar rich plants in a fermentation plant. The advantages of PHA for grocery bags include its good tensile strength, heat sealability, low molecular weight, good oxygen permeability, good ultra-violent resistance, temperature stability, resistance to grease and oil, and its barrier to flavour and odour. It is also water soluble and, most importantly, it is able to fully degrade into carbon dioxide and water to leave no environmentally harming waste. However, there are also several disadvantages, including the poor resistance of PHAs to acids and bases, the solubility of PHAs in chloroform and other chlorinated hydrocarbons, and the high production cost in PHA manufacturing.

In its premanufacturing stage, corn, water, and bacteria are used to produce PHA. Solid wastes such as corn cobs, grits, and dead Alcalugenes Eutrophus are produced. These solid residues are degradable or reusable. However, various process machines and technologies use electrical energy, with energy used in the manufacturing process of PHA being about 31,218 kilojoules per kilogram of PHA produced, which is equivalent to 2.39 kilograms of fossil fuels.

Reusable paperboards are used for packaging to reduce solid wastes, which contribute to global warming. Moreover, small amounts of petroleum are used in the transportation of each bag, which also produces greenhouse gases.

In its use stage, aside from the carrying of goods, grocery bags can also be reused to carry sundry goods or as food wraps, garbage bags or other purposes. PHA grocery bags are fully degradable into water and carbon dioxide, leaving no harmful residues to the environment. However, transportation is needed in the disposal from household users to disposal fields which uses a relatively small amount of energy per bag. The degradation of PHA also results in emission of carbon dioxide during disposal.

Recommendations and Findings

Functionally, all three alternatives perform at or above the expectations of a user of the common grocery bag. Each of these bags can be used to transport and package merchandise, including groceries, as well as be used as an advertising mechanism for retailers, for disposal into public waste systems, and for storage. The main differences between the alternatives lie in their physical properties, which are due to the different raw materials and production processes each alternative uses. The use of petroleum and natural gas allows for polyethylene bags to be manufactured at a higher capacity than that of Mater-Bi and PHA, which primarily use resources from agricultural sources that have yet to be adapted to support large manufacturing systems and facilities. In addition, the production of PHA bags requires the use of special bacterium to synthesize the PHA material, which has yet to be optimized. The mechanical properties that are important to end users of the proposed alternatives are nearly identical, and as such, do not inflict noticeable change in their use of the various bags.

Environmental Effects

Streamlined Life Cycle Assessment for Grocery Bag Alternatives

The largest difference between the two proposed alternatives, Mater-Bi and PHA, and the baseline conventional product, polyethylene, is in their relative qualitative environmental impacts. As seen from the streamlined assessments of each alternative, the use phase involves no environmental impact. This is because the use phase of a grocery bag is considered to be very short, and involves no inputs or outputs from the bag itself. The largest discrepancies between the SLCA scores of each alternative are found with the Premanufacture and the Recycling and Disposal stages, with the discrepancies found primarily between the proposed alternatives and the baseline alternative. In the premanufacturing stage, it is clear that the use of fossil fuels and their higher greenhouse gas emissions contributed to the low score for polyethylene, and the higher dependence on the agricultural sector and its renewable products contributed to the higher scores for both PHA and Mater-Bi. This is despite the additional impact brought about by the transportation of Mater-Bi supplies overseas from Europe. Similarly, the biodegradable nature of the proposed alternatives gave both Mater-Bi and PHA the higher scores in the Recycling and Disposal life stage, as the polyethylene bags are known to take numerous years to decompose into its elemental components, whereas the alternative bags take less than one year to biodegrade itself in a compost environment.

When this qualitative assessment is compared to the quantitative assessment of the EIOLCA, environmental impacts of the PHA bag are found to be much greater than those of both polyethylene and Mater-Bi. It is reasonable to assume that this is due to the magnitude of the impact the agricultural sector imparts on the environment. The contribution to the global warming potential of PHA comes primarily from nitrous oxides. The source of these nitrous oxides is indeed from the agricultural sector, where the heavy use of soil and crop fertilizers causes large quantities of equivalent carbon dioxide emitted. Between the polyethylene and Mater-Bi alternatives, very small differences occur, with Mater-Bi demonstrating slightly lower environmental impacts, which are a result of the dependence of polyethylene on the petroleum and natural gas industries.

Economic Considerations

To the average consumer, the choice between polyethylene, Mater-Bi, and PHA grocery bags will generally come down to a matter of cost – both a cost to the end user and a cost to the retailer supplying the bags. In this area, it is clear that the polyethylene bag is still the most inexpensive alternative amongst the three analyzed. This is related to the existing and well-established mass production techniques for this bag, which is partly due to its existence in the consumer marketplace for over twenty-five years, and its dependence on a resource that has a history of involvement within the manufacturing sector, particularly in the area of mass production. The Mater-Bi bag is starting to approach the cost of polyethylene bags, as demand for these biodegradable bags continues to increase from consumer sentiments about the environment, and government regulations being enacted in recent months. The PHA grocery bag, still, however, is not an economically viable option, as the production process is not well established and its dependence on the agricultural sector, where increased demand of its own conventional products is of most importance.

Societal Preference

The recent introduction of legislation regulating the use or distribution of polyethylene grocery bags in various jurisdictions around the world has resulted in a demand for newer technologies, such as Mater-Bi and PHA, for the production of grocery bags. Coupled with these regulations is an overall consumer trend away from traditional bags. This is particularly evident with the introduction of reusable cloth bags by many retailers, which serve all the functions of the polyethylene bag, but also allow the retailer to sell the bag as a product itself, while introducing advertising that depicts the environmental conscience of the retailer and the loyalty of the user to the brand. However, for the average user, whose main concern is with functionality and cost, he or she would prefer the polyethylene bag being offered free of charge over a cloth bag offered for five or ten dollars more. As such, for retailers to maintain their customer loyalty and adhere to governmental regulations, it is obvious that the Mater-Bi, PHA, or any other biodegradable grocery bag beyond the scope of this report, will become entrenched into society.

Government officials around the world are taking initiatives to reduce the use of plastic bags by creating policies involving levies and bans, thereby reducing their environmental impact. In 2002, the Republic of Ireland placed a 15 cent tax per plastic grocery bag. Within five months, the use of plastic grocery bags was reduced by more than ninety percent. In 2005, the government of San Francisco, California applied a 17 cent tax of every plastic bag. In 2007, San Francisco also approved legislation to ban plastic bags at large supermarkets and chain pharmacies by 2008. Recently, Leaf Rapids, a small town in Manitoba, Canada also placed a ban on plastic bags. In the cases of San Francisco and Leaf Rapids, retailers are prevented from selling or distributing these single-use plastic bags. Similar taxes and bans on plastic bags have begun to take place in countries such as Germany, China, Kenya, Uganda, and Sweden.. Countries worldwide are expressing their concern over the environmental impact from plastic grocery bag use by looking to biodegradable bags and other alternatives.

Based upon 4800 consumer surveys conducted by NatureWorks, 41% of North American consumers ranked biodegradable bags as very desirable, with 74% of these respondents willing to pay 5 cents more and 60% willing to pay 10 cents more per bag . A case study conducted by Novamont at six GS Carrefour supermarkets in Italy showed that Mater-Bi bags were chosen over polyethylene bags because the product was biodegradable and could be recycled for organic waste with price as the least appreciated factor . Overall inclination to purchase was 70% of the 500 surveyed due to the perceived environmental benefits.

Recommendations

Summary of Relative Performance of Three Alternatives

EIOLCA and Conventional LCA Results Comparison

Based on this study and the work of others in this area of environmental analysis, it is clear that the Mater-Bi grocery bag is the best choice for the Canadian market and North American production. Its minimal impact to the environment and its positive impact on societal behaviour outweigh its slightly higher production costs, and therefore, can be considered superior to the lower-cost, environmentally unfriendly polyethylene, and the higher-cost, underdeveloped PHA.

Details of Polyethylene Plastic Bags

Economic Input-Output Life Cycle Analysis

Polyethylene Bags EIOLCA Economic Activity

The total value of economic activities in the plastic packaging material, film and plastic resin manufacturing represented more than half of the total economic activity. In addition, the total value of economic activities as a result of manufacturing the polyethylene bag is 250% of its retail value. Toxic releases are evenly distributed throughout the life cycle of the bag. There is a total of 158,000 kilograms of toxics released throughout the life cycle of 6 billion bags. Over half of these toxic substances are released into land and underground. Twenty-five percent of all toxic releases are produced during the manufacturing process of plastic resin and films. The majority of all sulfur dioxide (SO₂) released is from power generation, as coal is assumed to be the primary source for power generation. Moreover, a total of 1320 metric tons of carbon monoxide (CO) and 307 metric tons of nitrogen oxides (NO_x) is released from various sectors throughout the life cycle of plastic bag. Aside from the plastic resin manufacturing process, energy consumption is evenly distributed amongst the other sectors. However, the manufacturing process of plastic resin is energy intensive, and thus, this sector consumes relatively more energy than the other sectors combined. The amount of energy required to produce 6 billions plastic bags is 1910 terajoules. Finally, the global warming potential for annual Canadian plastic bag consumption is estimated at 146,000 metric tons of equivalent carbon dioxide (CO2).

Polyethylene Bags EIOLCA Results

Cost Analysis

Polyethylene plastic bags are made mainly from crude oil or natural gas. For the purpose of this study, crude oil is assumed to be the only resource used to manufacture the bags. The average price of crude oil is estimated at $74.00 USD per barrel in 2007 . As such, the cost of raw material per polyethylene bag is approximately $0.0103 USD. Within the plastic bag manufacturing stage, the estimated total materials and supplies, and fuel cost for 6 billion plastic bags in 2007 is $376 million USD in Canada, thus the direct cost per bag is approximately 0.0627 USD.

There are crude oil and natural gas refineries in the Canada and more than twenty-five plastic bag manufacturers within the Greater Toronto Area for which truck is the primary transportation method used for plastic bag and found to have negligible affect on the cost per bag . Although many retailers give plastic bags to their customers free of charge, the cost to retailers is an estimated $0.03 per bag USD.

Disposal of plastic bags has a direct cost based on the recycling and composting program cost of $135 USD per metric ton in Toronto, of $5.7 million USD for the Canadian annual demand of 6 billion plastic bags.. The indirect cost of plastic bag as a result of litter or other inappropriate garbage disposal methods include the cost to natural habitats of wild animals. For example, Marine animal rescue shelter in Texas, US discover a large proportion of sea turtles that die are as a result of ingesting plastic bags . Based on a cost-benefit analysis from the Roosevelt Report, the social cost for every plastic bag sold is more than thirty cents per bag.

Details of Mater-Bi Plastic Bags

Economic Input-Output Life Cycle Analysis

Mater-Bi EIOLCA Economic Activity

Each bag produces $0.11 US (1997) of economic activity, 33% of which is in the resin manufacturing, film packaging and wet corn milling sectors. This was found for an economic input of $213 million USD (1997) for the current Canadian demand of 6 billion bags per year. The energy intensive sectors - power generation and supply (21% GWP, 22% Energy) and agriculture (grain farming 15% GWP and wet corn milling 9% GWP, 16% Energy) - are the largest sources of greenhouse gas CO2 emissions due to the raw resources extraction required in both processes.

Transportation of Mater-Bi pellets overseas from Italy to Canada also has significant environmental impact (6% GWP, 8% Energy) due to the amount of fuel required for freight air transportation. The premanufacturing of the Mater-Bi pellet in the custom plastic material and resin manufacturing sector is the second most energy intensive process requiring 901 terajoules, or 16% of the overall total, and has the highest amount of toxic air, water and land releases at 66,200 kilograms.

Sensitivity analysis of the results showed that a 25% increase in cornstarch content in Mater-Bi would lead to 8.1% increase in global warming potential and 5.2% increase in energy from agriculture activities. The true production cost was not released by Novamont and variation in estimated values is in direct relation to the environmental impact found using the EIOLCA.

Mater-Bi EIOLCA Results

Cost Analysis

Mater-Bi pellets are marketed at between $2.50 to $8 USD per kilogram to processors including BioBag, the largest bioplastic bag manufacturer in the world. The retail prices of Mater-Bi bags are estimated between five and fourteen cents per bag . A five cent bag cost was assessed for a Canadian demand of 6 billion bags per year if Mater-Bi biodegradable bags were to completely displace polyethylene bags in the market . This is for analysis purposes only as the maximum capacity at Novamont is 60,000 metric tons worldwide. A kilogram of Mater-Bi pellets can produce up to 109 bags (9.15 grams per bag), in comparison to 142 polyethylene bags (7 grams per bag) using film extrusion. The total pellet cost at $3.77 USD per kilogram would be $207 million USD or 60% of the total bag cost of $345 million USD. Delivery cost overseas via air or water transportation contributes to $30 million USD, accounting for 10% of direct costs.

The indirect cost of Mater-Bi bags is based upon its benefit compared to polyethylene bags during its end of life. The health, air pollution and environmental cost of each non-biodegradable bag represented by the external costs of SO2, NOx, PO4, global warming potential and other releases is accounted for in levies. The environmental cost is estimated to be 10 cents per bag based on levies ranging from 15 cents in Ireland to 5 cents for purchases at furniture retailer IKEA. The indirect cost benefit from the levy saved is $372 million USD which is greater than the direct cost of $291 million USD for the annual consumption in Canada.

Details of PHA Plastic Bags

Economic Input-Output Life Cycle Analysis

PHA EIOLCA Economy Activity

For an economic input of $449 million USD for 6 billion bags in 1997, 31% of the production cost of PHA ($377 million) is attributed to the grain farming sector, 5% of the cost is attributed to the agriculture and forestry support activities sector, 43% of the cost is attributed to the wet corn milling sector, and 20% is attributed to the “All other industrial machinery manufacturing” sector.

From the EIOLCA result plots, it can be seen that the power generation and supply sector contributes to most of the toxic releases. This is caused by the large amount of energy and power used during the fermentation process in the production of PHA polymers from glucose. It can also be seen that the power generation and supply sector uses 40% of the total energy. Also, a comparative amount of this energy and power is used in the transportation of materials, distribution of products, and the disposal of products. The other area that contributes to the pollution is the pesticide and other agricultural chemical manufacturing sector, since a reasonable amount of pesticides is used during the farming of corn which is a comparatively high amount of pollution.

From the total global warming potential chart, it can be seen that grain farming produces the most greenhouse gases. This can be explained by the high energy use in the machinery used in farming which comes from the burning of fossil fuels and produces greenhouse gases.

From the total energy consumption chart, it can be observed that wet corn milling also contributes to 20% of the overall energy usage. Similarly, its main sources of energy come from coal and natural gases. The burning and mining of these two energy sources both produces greenhouse gases and toxic residues which causes air pollutions and global warming.

PHA EIOLCA Results

Cost Analysis

For the cost analysis, the profit margin for the pellet supplier is approximately 30% , the inflation rate is 1.292, and all costs are converted into the value of year 1997 for comparison. The average material cost per bag is calculated to be $0.0441. The retail price of the PHA grocery bag is approximated to be $0.09676 USD per bag . Therefore, the manufacturing cost per bag in 1997 would be $0.0308. The total delivery cost per bag is $ 0.00016, and the total disposal cost is about $0.00011.

The indirect cost is calculated as the reduction in oil imports for petrochemical plastics base on the fact that 50 billion pounds of PHA production would reduce oil imports by 215 million barrels per year and assuming the oil price is at $35 per barrel. Therefore, the indirect cost reduction per bag in the value of 1997 would be $0.00127.

References

Books

• C. Bastioli (2005). Handbook of Biodegradable Polymers, Rapra Technology. ISBN 9781859573891
• M. Biron (2007). Thermoplastics and Thermoplastic Composites: Technical Information for Plastic Users, Elsevier Science. ISBN 9781856174787.
• T. E. Graedel (1998). Streamlined Life Cycle Assessment, Prentice Hall. ISBN 9780136074250
• C. T. Hendrickson, L.B. Lave, and H. S. Matthews (2006). Environmental Life Cycle Assessments of Goods and Services An Input-Output Approach, RFF Press. ISBN 9781933115245
• M. L. McKinney and R. M. Schoch (2003). Environmental Science: Systems and Solutions, Jones and Bartlett Publishers. ISBN 9780763709181
• E. S. Stevens (2002). Green Plastics: An Introduction to the New Science of Biodegradable Plastics, Princeton University Press. ISBN 9780691049670
• M. Finklestein and B. H. Davison (1998). Biotechnology for Fuels and Chemicals. Applied Biochemistry and Biotechnology. Humana Press. ISBN 0896036510
• S. Kim and B. Dale (2004). Life Cycle Assessment Study of Biopolymers (Polyhydroxyalkanoates) Derived from No-Tilled Corn. Michigan State University. ISBN 0849334667

See also

• Design for the Environment

it is very good for the enviroment and when it gets old you can recyle it